Gas charging apparatus



Sept. 10, 1957 Filed March 51 1955 c. T. DE GROAT 2,805,689

GAS CHARGING APPARATUS 2 Sheets-Sheet l 4 INVENTOR: Ix CHARLES T.DEGROAT,

Sept. 10, 1957 c. T. DE GROAT 2,805,689

GAS CHARGING APPARATUS Filed March 31, 1955 2 Sheets-Sheet 2 I'NV'ENTORICHARLES T. DEGROAT,

HISA ORNE United States Pate GAS CHARGING APPARATUS Charles Thomas DeGreat, Ballston Lake, N. Y., assigner to General Electric Company, acorporation of New York Application March 31, W55, Serial No. 49%,209

1'7 Claims. (Cl. 141-66) My invention relates to improved evacuating andgas charging apparatus of a type which is particularly adapted for themanufacture of small volume evacuated devices, such as vacuum tubes,transistors, and the like.

In making gas filled devices or in gas charging or loading devices fortreating internal atmospheres, elements or surfaces thereof,considerable difliculty has been generally encountered in providingapparatus for eflectively introducing the gas into the devices followingevacuation thereof without wasting a volume of gas substantially largerthan that actually used. When the gas to be loaded is xenon or someother expensive gas, waste of this kind can prove extremely costly.Additionally, difiiculty has been experienced as a result ofcontamination of the gas in the charging system due to defective orleaking tubes or an unloaded or open tube port on the equipment.

In my United States Patent No. 2,542,636 issued February 20, 1951, andassigned to the same assignee as my present invention, I have disclosedan improved automatic evacuating and gas charging apparatus which hasproved completely effective in overcoming both of the abovementioneddifi'iculties when the devices charged or loaded with gas volumes in theorder of ten cc. and larger and the loading or charging is to pressuresof 200 microns and higher. Many evacuated devices currently beingproduced, however, such as those referred to in the art as sub-miniatureelectronic tubes, transistors, etc. have volumes less than cc. and aslittle as 1 cc. and are required to be gas filled or charged topressures as low as approximately 25 to 200 microns. Additionally, thesedevices are generally produced on high speed equipment such as thatknown in the industry as the Sealex machine. On such equipment eachdevice dwells in an operating station for only a very short period. Thisnecessitates the provision of equipment or apparatus which will not onlygas charge a device quickly but will also purge the system ofcontamination substantially immediately upon detection of a leak to theatmosphere and will recover substantially immediately thereafter inorder to stand ready to gas charge a succeeding device at the desiredpressure and thereby avoid spoilage of other devices due tocontamination of the system caused by a leak.

Accordingly, the primary object of my invention is to provide a new andimproved gas charging system.

Another object of my invention is to provide a new and improvedevacuating and gas charging apparatus.

Another object of my invention is to provide a new and improved gascharging apparatus adapted for effectively gas charging devices ofvolumes down to approximately 1 cc. and at pressures as low as 25microns.

Another object of my invention is to provide new and improved gascharging apparatus including a charging system adapted for being purgedof contamination substantially immediately upon detection of a leak andfurther adapted for recovering substantially immediately followingpurging.

Still another object of my invention is to provide gas chargingapparatus which is suitable for use in any type ice 2 of processingequipment but has all the attributes necessary for use with high speedequipment.

Further objects and advantages of my invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming part of this specification.

In carrying out the objects of my invention I provide a controlled gassupply system adapted for having devices to be charged connected insealed communication therewith. Adjustable control means is provided forreplenishing the controlled gas supply from a reservoir upon reductionof the pressure therein below the minimum pressure of a predeterminedpreset range and until the maximum pressure of the predetermined presetrange is attained. Other control means are provided and are effectivefor substantially immediately closing the controlled gas supply systemto the reservoir and evacuating the controlled gas supply systemsubstantially immediately upon a pressure increase above the maximumpressure of the present range and subsequently substantially immediatelyrestoring the controlled gas supply to the predetermined pressure range.A gas pressure gauge including a pressure chamber substantially equal involume to one of the devices to be charged is adapted for beingconnected to the controlled gas supply while the adjustable controlmeans is adjusted and until the gauge reads a pressure corresponding tothat desired to be obtained in devices to be charged. Additionally,means is provided for purging the controlled supply system and thereservoir.

For a better understanding of my invention reference may be had to theaccompanying drawing in which:

Fig. 1 is a schematic illustration of my invention; and

'Fig. 2 is an enlarged sectional view of the adjustable control valve inmy system.

Referring now to Fig. 1 of the drawing, I have shown my inventionembodied in an automatic exhaust and gas charging machine of the typegenerally known in the industry as a Sealex machine and adapted forproducing electric discharge devices. The machine includes a pluralityof identical exhaust heads generally designated 1 and supported on amoveable support or turret 2 which is rotatably mounted on a stationarysupport or machine frame 3. In a practical machine embodying myinvention, sixteen exhaust heads 1 are provided at equally spaced pointsaround the turret 2. Only two of the heads are shown in the drawingtosimplify the illustration and description.

It will be appreciated that the moveable turret is moved intermittentlyby a suitable indexing system (not shown), thereby to position theexhaust heads successively at a plurality of operation stations locatedspacedly about the machine. It will be further appreciated that in veryhigh speed equipment the turret may move continuously instead ofindexed. Each of the heads 1 includes an exhaust chamber 4. The bottomside of the chamber 4 is adapted for being closed by a valve 5. Thevalve 5 may be any suitable valve such as a pinch-off valve formed ofrubber or any similar material. The valve 5 is connected to one end ofan exhaust line 6 and is adapted for being operated rubber valve forthereby closing the chamber 4 to the line 6. In another rotativeposition of the cam 7 the natural resilience of the valve 5 prevents theclamp 10 from clos- Patented Sept. 10, 1957.

ing the valve and thus communication is afforded between the chamber 4and the line 6.

The heads 1 each further include a compression head generally designated13 and adapted for being operated to grip and maintain or hold theexhaust tubulation 14 of an electronic tube or device 15 to be exhaustedand gas charged in sealed communication with the chamber 4. It will beseen that while I have shown an electronic tube 15 held in the exhaustheadv any device to be eX-.,

hausted and gas charged and provided with a suitable tubulation may beheld in place in communication with the exhaust chamber by thecompression head 13. It will be seen further that my invention is notlimited to the processing of tabulated devices. For example, it may beused in the processing of evacuated devices in bell-jet arrangements.Additionally,,each of the heads 1 includes a gas charging port to whichis suitably connected a line 21 which extends toward the center of themachine. This arrangement and the purpose thereof will be brought out indetail hereinafter.

From the heads 1 the lines 6 extend toward the center of the machine andare each connected to one of a plurality of inlet ports 22 (only one ofwhich is shown) formed in suitably spaced relation in a rotatableportion 23 of a rotary valve generally designated 24. The rotatableportion 23 is mounted about and suitably secured to a central hub 25formed on the turret 3 and rotatably mounted on a central vertical pivotpost of the frame 3. A stationaryportion 26 of the valve 24is suitablysecured to the stationary frame 3. Additionally, the stationary portion26 of the valve is formed to include a plurality of outlet ports 27(only one of which is shown) corresponding in number and spacing to theinlet ports 22 in the rotatable portion of the valve. The rotary valveis further constructed to include a pluralityof suitable oil glands 30on both the inner and outer sides of the ports 22 and 27, thereby torender the valve vacuum-tight.

The operation of the just-described rotary valve is such that in each ofthe indexed positions of the turret 2, one

of the inlet ports 22 in the rotary portion 23 of the valve is incommunication with one of the outlet ports 27 in the stationary portion260i? the valve for permitting fluid passage therethrough. Betweenindexed positions, the p0rts22 and 27 are all out of alignment orregister. and communication and fluid passage across the valve isprevented.

At several of the operating stations at which the heads are indexed thedevices 15 are adapted for being exhausted.

or evacuated. To accomplish this and in advance of the exhaust stationsstationary camming means (not shown) on the machine frame 3 is effectivefor engaging and actuating the cam 7 of each head 1 as it movestherepast, thereby to open the valve 5 in the head. Additionally, atthese stations the corresponding outlet ports 27 of the rotary valve 24are suitably connected, as by an arrange ment of a manifold and linegenerally designated 31, t0 vacuum pumping means such as that generallydesignated 32 and suitably mounted'on the stationary frame 3 of themachine. Thus, the devices 15 carried in the heads 1 are adapted forbeing exhausted at one or more of the various indexing or operatingstations of the machine.

After being positioned at the various operating stations whereatexhaustion occurs each head lmoves to a tip-off station (not shown),whereat the tubulation 14 of the tube or device 15 held in the head issuitably sealed off. By means not shown and in advance ofthe tip-0Estation, the cam 7 is rotated or actuated for closing the head valve 5.r My invention, as applied to the machine illustrated andabove-described is adapted for gasfilling or charging each tube ordevice 15 just before tip-off and after the valve 5 is closed, andpreferably on-the-fiy between the station immediately preceding thetip-off station and the tip-off station. I find it preferable to chargethe tube on-the-fly before tip-off inasmuch as thisallows the gasgreater time tion 23 of the rotary valve 24 and disposed radiallyinwardly of the corresponding exhaust inlet ports 22.. Provided forcooperating with the ports 35 is a single port 36 formed in thestationary portion 26 of the rotary valve between the two outlet ports27 corresponding to the tip-otf station and the station immediatelypreceding the tip-off station. Thus, just before each head 1 moves intothe tip-off station and after the pinch-off valve 5 is closedcommunication is provided to the exhaust chamber 4 of the head throughthe line 21 and across the valve arrangement comprising thecorresponding port 35 in the rotatable portion of the rotary valve andthe single port 36 in the stationary portion of the valve.

Port 36 is connected to a controlled gas supply system generallydesignated 40 and comprising a line 41 connected to a terminal block 42,a line 43 connected to a pressure sensitive device or control 44, apressure chamt her 45 in the device 44, a line 46 connected to 8.normally closed solenoid controlled vacuum valve 47, and a line 48connected to the outlet side of an adjustable control valve generallydesignated 50. i

As perhaps better seen in Fig. 2, the adjustable control valve 50comprises a housing 51 suitably mounted on the frame 3 and formed toinclude an upstanding or raised valve seat 52. The valve seat 52includes a substantially frusto-conical internal surface 53;and providedfor cooperating with the surface 53 is a frusto-conical portion 54 of avalve pin or needle 55. The surfaces 53 and 54 are lapped and in theclosed position of the needle the upper end thereof is as perfectly evenwith the upper.

edge of the valve seat 52 as possible. Formed on the pin 55 is anenlarged portion 56 further formed to provide a suitable sealing surfacefor cooperating with an O-ring seal 57 for avoiding leakage across thevalve pin. The lower end of the valve pin 55 is fixedly secured in thecenter of a worm wheel 58 suitably rotatably mounted in the lower sideof the housing 50. Meshing with the worm wheel 58 is a worm 59. Fittedin oneend of the worm and extending through the housing wall is a stemcarrying a knurled knob 59a. With this, arrangement very fine.adjustments may be madeto the position. of the valve pin in the valve.seat. thereby to control with a high degree of accuracy any gas.supplied through the valve 50 and into the controlled gas supply system40.

Also included in. the valve 50 is an on o arrangement including a coil60, a magnetic plunger 61 and a coil spring 61a normally biasingtheplunger 61 toward the valve seat 52. The lower, end of the plunger. 61is fitted with a resilient cap 62 adapted for moving into and out ofengagement with the valve seat 52 for closing the valve undertheiniluence ofthe spring 61a when the coil is deenergized and for.being raised from the valve seat and opening the valve when the coil isenergized.

Connected to the inlet side of the valve 50 by means of a line 63 is agas reservoir 64 adapted for being supplied with a suitablegassuch asxenon from a tank thereof 65. The gas is supplied from the tank to thereservoir through a pressure regulator 66 and a solenoid controlledvalve 67 which is mounted on the frame 3 and controlled by abellowoperated switch 68. The switch 68 is usually set at approximately1200 millimeters or just slightly above atmospheric pressure asindicated on a dial, type pressure gauge 69 connected to a reservoir 64.

The pressure of the gas admitted into the system 40 through the valveSOIdetermines the operation ofv the above-mentioned pressure sensitivecontrol 44; The control 44 may be of any suitable type, for.detectingpressure changes and providing suitable. proportionalelectrical signals. For example, when xenon or other heavy gases areused an ionization type gauge such as an Alphatron Vacuum Gauge of thetype designated 510 and manufactured by the National Research Company ofBoston, Massachusetts, may be used. If lighter gases, such as hydrogenor helium are used, the device or control 44 may comprise athermo-cond-uctivity gauge of the thermocouple or Pirani types and whichare well-known in the art. Additionally, the control 44 is adapted foroperating in unison with a pressure recorder or recording controllergenerally designated 70 and which may be of the type designated Type 153Electronik Recorder manufactured by the Brown Instruments Division ofthe Minneapolis- Honeywell Regulator Company of Philadelphia, Pennsyl-Vania.

The recorder or recording controller 70 is adapted for receivingelectric signals of varying magnitudes from the pressure control 44. Inthe controller 70 these signals operate an electromotive device 71 whichactuates a marker 72 adapted for cooperating with a scroll 73 arrangedto move in coordination with the operation of the machine. Also includedin the controller 70 is a shaft 74 carrying a plurality of control disks75 and adapted for rotating and counter-rotating in accordance with themovement of the marker 72. In a manner which will be described in detailhereinafter, the pressure in the system 40 is normally caused tofluctuate between the high and low values of a predetermined presetpressure range. This causes the marker 72 to scribe a substantiallysymmetrical mark designated A on the scroll and the shaft 74 and theplurality of control disks 75 to assume positions substantially the sameas those shown in Fig. 1. When the pressure in the system exceeds theupper value of the preset range, the marker moves to the right of A andthe shaft and disks are caused to rotate clockwise from the positions ofFig. 1. When the pressure falls below the lower level of thepredetermined range the marker 72 moves to the left of A and the shaftand disks are causedv to rotate counterclockwise from the positions ofFig. l.

The disks 75 comprise three independent controlling disks. The firstdisk designated 80 operates a mercury switch 81 and is positioned on theshaft 74 for opening the mercury switch when the pressure in the system40 stands above the lower level of the predetermined range. When thepressure in the system 40 falls below the lower level of thepredetermined pressure range the control 44 varies the magnitude of thesignal of the recorder 70 which causes the shaft'74 to rotatecounterclockwise and r the disk 80 thereon to actuate and close themercury switch 81. This results in completion of a circuit through anormally closed pair of contacts 82 in a relay 83. This circuit whencompleted energizes the coil 60 in the control valve 50 for raising theplunger 61 against the bias of the spring 61a and thereby admitting gasinto the system 40 from the reservoir 64.

When the system 40 attains the upper level of the predetermined pressurerange, the control 44 again varies the signal to the recorder 70 whichcounter rotates the shaft 75 causing the disk 80 to open the mercuryswitch 81 and thereby deenergize the coil 60 for enabling the spring 61ato move the plunger 61 toward the valve seat 52 and close the valve 50.This is the operation of the system under normal operating conditions.That is, as the gas port of the rotary valve associated with eachexhaust head 1 flies or moves past the stationary port 36 a quantity ofthe gas in the controlled supply system is admitted through thecorresponding line 21 and exhaust chamber 4 into the device 15 held inthe head. In accordance with the volume of the devices being charged thepressure in the system40 is reduced by substantially equal increments.Ultimately, this pressure is reduced to the pressure where-the disk 80is again effective for closing the mercury switch 81 and thereby openingthe valve for admitting more gas from the reservoir into the system 40for again raising or restoring the controlled pressure to the upperlevel of the predetermined range.

It will be seen that through adjustments to the valve 50 I am able todetermine with extreme accuracy the amount of gas admissible into thesystem 40 when the valve 50 is opened. Additionally, by presetting thepressure control 44 and presetting the position of the disk on the shaft74 I am able normally to maintain the pressure in the system 40 within apreset predetermined pressure range. For example, when it is desired tocharge devices of a volume of approximately 1 cc. to a pressure ofapproximately 25 microns the valve 50 may be adjusted and the control 44and the disk 80 may be preset for closing the valve 50 when the pressurein the system 40 stands at approximately 500 microns, which wouldrepresent the upper level of the normal range, and opening the valve 50when the pressure stands at the lower level of the range which may be 5%below the upper level. The pres sure in the system 40 will drop to thelower level of the predetermined range after a predetermined pluralityof the devices 15 have been moved into and out of communication with thesystem and thereby charged with gas to the prescribed pressure.

Now in the event of a leak into the system 40 from the atmosphere, asmight be effected by a leaking device 15 in" one of the heads 1, it isdesirable to detect such a leak, close the valve 50 to avoid waste ofgas, purge the controlled gas supply system 40 and restore the pressurein the controlled gas supply system 40 to the preset pressure range allbefore the port 35 corresponding to the next succeeding head moves intoregister with the stationary port 36, thereby to avoid spoilage of thedevice of the next succeeding head. To accomplish this I have provided asecond control disk 85 on the recorder shaft 75. The disk 85 is adaptedfor closing a normally open mercury switch 86 when the pressure control44 senses a pressure increase in the system above the upper level of thenormal or predetermined preset pressure range, as would be effected by aleak or open head. The switch 86 when closed energizes the coil 87 ofthe relay 83 whereby the normally closed contacts 82 are opened fordeenergizing the coil 60 in the event the latter is energized andassuring that the plunger 61 is in its lower position for closing thevalve 50.

Additionally, energization of the coil 87 results in the closing of apair of normally open contacts 88 which is effective for energizing theabove-mentioned normally closed vacuum control solenoid valve 47 forthereby opening the valve 47. The outlet side of the valve 47 isconnected by a suitable line 90 to a constantly operating vacuum pumpgenerally designated 91 and suitably mounted on a portion of the machineframe 3. The pump 91 is of such capacity as to evacuate and therebypurge the system 40 of contamination completely substantiallyimmediately or well within the time required for movement of an exhausthead 1 from one operating position to the immediately next succeedingpositions This evacuation of the system 40 results in a correspondingmovement of the shaft 75 in the controller 70. Provided on the shaft 75to take advantage of this movement is a third controlling disk 95. Thedisk 95 operates a mercury switch 96 which is normally closed above apreset minimum pressure below the predetermined range and correspondingto a satisfactorily low purging pressure.

The circuit completed by the switch 96 maintains the coil 87 energizedand thus maintains the vacuum valve 47 open after the pressure in thesystem is reduced to the point where the switch 86 is normally openedand until the pressure is reduced by the pump 91 to the preset minimumvalue at which the switch 96 will open. Opening of the switch 96deenergizes the coil 87 whereby the contacts 88 are opened and thecontacts 82 are closed. At

this "stage of the operation, inasmuch as the pressure in the system 40will be below the predetermined preset pressure range, the disk 80 .willbe .eltective for closing the switch81 and thereby resulting in acircuit being.

completed through the normally closed contacts 82 and the coil60 in thecontrol 50 thereby to open the valve 50 and permit the: pressure in thesystem 40 to return to the normal preset maximum pressure. Thus, mysystem is adapted for avoiding contamination of the next succeedingdevice 15 moved into communication with the system 40 following aleaking device or open head.

When devices of predetermined volume are to be processed by the. machineand gas charged, I set up the machine byinserting a tube 97 in one ofthe heads 1 instead of the tubulation of a device to be charged. Thetube 97 is connected to a pressure gauge generally designated 98 andsuitably secured to the turret 2. By means of a pair of brushes 99resiliently contacting a pair of commutator rings 100 mounted on therotatable hub 25 of the turret and connected to a suitable power source,the gauge 98 is provided with required power for operation. The gauge 98may be of any suitable type. For example, when xenon or other heavygases are used the gauge may be of this ionization type similar tothatmanufactured by the National Research Company of Boston and designatedACXB-l Alphatron-Miniature cylinder. If lighter gases, such as helium orhydrogen,

pressure at which it is desired that the devices 15 be gascharged at theparticular operating speed of the machine. With this accomplished thecontrol gas supply system 40 will stand at the maximum pressure ofthedesired or preset normal pressure range. While it is possible to set upthe machine in this manner and then remove the tube 97 from the exhausthead in order that this head may be used for processing a device 15, itis often found desirable to leave the tube 97 in the head and therebyhave a con stant check on the pressure to which the devices are be ingcharged; Additionally, gauges of different chamber volumescorrespondingto the volumes of different sized devices to be charged may. beprovided. Thus, in accordance with the volume of the devices to beprocessed on the machine the proper gauge arrangement may be used insetting up the machine.

Aftera shut-down of the machine of any length of time, the systemincluding the reservoir 64 is likely to be contaminated. Thus, ininitially setting up the ma- "chine for operation an operator will openthe power line to the switch .68 for deenergizing and thereby closingthe reservoir control valve 67 to avoid waste of gas and then turn theknob 59a to move the needle in the valve 50-to its lowest position andclose a key type switch 101. With the. switch 101 closed a lamp 102 willlight indicating that purging is taking place and the relay coil 87 willbe energized for closing a pair of contacts 103 and the contacts 88 andopening the contacts 82. This will cause energization of both thecontrol valve 50 and the vacuum valve 47 for opening the system 40 andthe reservoir 64 to the constantly operating vacuum pump 91 whereby thesystem 40 and the reservoir 64 are purged. Then the operator will openthe switch 101,

and then energize and thereby oven the valve 67. This will enable thevalve 47" to close and the vacuum pressure control 44 to sense apressure lower than the minimum predetermined pressure below the presetpressure range.

Infturn, this will allow the system to recover and bev sup plied with.gas up to the predetermined range in the abovedescribed manner.Thereafter, the knob 59a may be turned to obtain a fine adjustment ofthe gas admitted through the valve 50 when it is energized and openedand the system will stand ready to charge the first device moved intocommunication with the system to the desired pressure.

It will be seen that while I have disclosed myinvention as applied tofully automatic tube processing equipment,

my invention is equally adaptable to bench systems or the like whereinmy invention may be operated manually or semi-automatically.

Additionally, while I have shown and described a specific embodiment ofmy invention, I do not desire my invention to be limited to theparticular form shown and described and I intend by the appended claimsto cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In gas charging apparatus, a gas supply system adapted for beingconnected to a device, thereby to charge said device, means normallymaintaining the gas pressure in said system within a predeterminedrange, and pressure-controlled means operative for evacuating saidsystem in response to any abnormalincrease in pressure above saidpredetermined range.

2. In gas charging apparatus, a gas supply system adapted for beingconnected to a device, thereby to charge said device, means normallymaintaining the gas pressure insaid system within a predetermined range,pressurecontrolled meansoperative for evacuating said system in responseto any abnormal increase in pressure above said predetermined range, andmeans restoring said pressure in said system to said predetermined rangeupon evacuation of said system to a predetermined pressure below saidrange.

3. In ga's charging apparatus, a gas supply system, means admittinggassto said system until the pressure therein attains the upper level ofa predetermined range in which a device connected to said system ischargeable only to a predetermined desired final pressure, means forsuccessively connecting devices to said system, thereby to charge saiddevices, and means effective when pressure in said system stands at thelower level of said predetermined range for restoring said: pressure tosaid upper level.

4.'In. gas charging apparatus, a gas supply system, means admitting. gasto said system until the pressure therein attains the upper level of apredetermined range, means for successively connecting devices to saidsystem, thereby to charge said devices, pressure-response meansefiective when pressure in said systemstands at the lower level of saidpredetermined range for restoring said pressure to said upper level, andmeans forevacuating said system in response to an increase in pressureabove said upper level of said range.

5. In gas charging apparatus, a gas supply system, means admitting gasto said system until the pressure therein attains the upper level of apredetermined range, means for successively connecting devices to saidsystem thereby to charge said devices, and means effective when pressurein said system stands at the lower level of said predetermined range forrestoring said pressure to said upper level, means for evacuating saidsystem in response to an increase in pressure above said upper level ofsaid range, and means for terminating. said,evacuation and restoringsaid pressure in said systemto said upper level of said range when saidpressure in said system stands at a predetermined minimumpressure belowsaid range.

6. In evacuating and gas charging apparatus, a gas supply system, .meansfor successively exhausting a device and connecting said device to saidsupply. system, thereby to charge said device, pressure-responsive meansnormally operative for maintaining the gas pressure in said system at apredetermined range, and pressure-controlled means '9 for evacuatingsaid system in response to any abnormal increase in pressure above saidpredetermined range.

7. In evacuating and gas charging apparatus, a gas supply system, meansfor successively exhausting a device and connecting said device to saidgas supply system, thereby to charge said device, means for maintainingthe gas pressure in said system within a predetermined range, means forevacuating said system in response to any increase in pressure abovesaid predetermined range, and means restoring said pressure in saidsystem to said pre: determined range upon evacuation of said system to apredetermined level below said range.

8. In gas charging apparatus, a gas supply system adapted for havingdevices to be charged connected thereinto, a gas reservoir, a controlvalve responsive to pressure conditions in said system for admitting gasinto said system from said reservoir, means normally operating saidcontrol valve for maintaining the pressure in said gas supply systemwithin a predetermined operating range, vacuum pumping means, and meansclosing said control valve and connecting said system and vacuum pumpingmeans in response to any abnormal increase in pressure in said systemabove said operating range.

9. In gas charging apparatus, a gas supply system adapted for havingdevices to be charged connected thereinto, a gas reservoir, a controlvalve for admitting gas into said system from said reservoir, meansautomatically operating said control valve for maintaining the pressurein said system within a predetermined operating range, vacuum pumpingmeans, means automatically closing said control valve and connectingsaid system and vacuum pumping means in response to any increase inpressure in said system above said operating range, and meansautomatically disconnecting said system and pumping means and openingsaid control valve for restoring said pressure to said predeterminedoperating range upon a decrease in pressure in said system to apredetermined pressure below said operating range.

10. In gas charging apparatus, a gas supply system adapted for havingdevices to be charged connected thereinto, a gas pressure gaugeincluding a pressure chamber having a fixed volume substantially thesame as the volume of one of said devices to be connected into saidsystem, a gas reservoir, a control valve for admitting gas into saidsystem from said reservoir, means automatically operating said controlvalve for maintaining the pressure in said system within a predeterminedoperating range, and adjusting means for varying said operating range inaccordance with the pressure desired to be obtained in said devices andas indicated by said pressure gauge.

11. In gas charging apparatus, a gas supply system adapted for beingconnected to an evacuated device thereby to charge said device,pressure-responsive means operative for normally maintaining the gaspressure in said system within a predetermined operating range, andevacuating means of substantially greater capacity than said systemeffective in response to any increase in pressure above saidpredetermined operating range for substantially immediately evacuatingsaid system.

12. In gas charging apparatus, a gas supply system adapted for beingconnected to an evacuated device thereby to charge said device, meansfor normally maintaining the gas pressure in said system within apredeter mined operating range in which a device connected to saidsystem is initially chargeable only to a desired final pressure, and aconstantly operating vacuum pump of substantially greater capacity thansaid system effective in response to any increase in pressure above saidpredetermined pressure for substantially immediately evacuating saidsystem.

13. In gas charging apparatus, a gas supply system adapted for havingdevices to be charged connected thereinto, a gas reservoir, a controlvalve for admitting gas into said system from said reservoir,pressure-responsive means normally operating said control valve formaintaining the pressure in said system within a predetermined operatingpressure range, a constantly operating vacuum pump of substantiallygreater capacity than said system. a normally closed vacuum valvecontrolling a connection between said pump and system, andpressure-responsive means closing said control valve and opening saidvacuum valve in response to any abnormal increase in pressure in saidsystem above said operating range whereby said vacuum pump is efiectivefor substantially immediately evacuating said system.

14. In gas charging apparatus, a gas supply system adapted for havingdevices to be charged connected thereinto, a gas reservoir, a controlvalve for admitting gas into said system, means automatically operatingsaid control valve for normally maintaining the pressure in said systemwithin a predetermined operating range, a constantly operating vacuumpump of substantially greater capacity than said system, a normallyclosed vacuum valve controlling a connection between said pump andsystem, means automatically ciosing said control valve and opening saidvacuum valve in response to any increase in pressure on said systemabove said operating range whereby said vacuum pump is efieictive forsubstantially immediately evacuating said system, and meansautomatically closing said vacuum valve and opening said control valvefor restoring said pressure to said predetermined operating range upon adecerase in pressure in said system to a predetermined pressure belowsaid operating range.

15. In gas charging apparatus, a gas supply system, for having devicesto be charged connected therein, a gas reservoir, means for supplyinggas to said reservoir, 'a control valve for admitting gas .into saidsystem from said reservoir, means automatically operating said controlvalve for normally maintaining the pressure in said system within apredetermined operating range, a constantly operating vacuum pump ofsubstantially greater capacity than said system, a normally closedvacuum valve controlling a connection between said pump and system,means automatically closing said control valve and opening said vacuumvalve in response to any increase in pressure on said system above saidoperating range whereby said vacuum pump is efiective for substantiallyimmediately evacuating said system, and manually operable means fordisconnecting said reservoir and said means for supplying gas theretoand for opening both said vacuum and control valves, thereby to purgesaid system and reservoir.

16. In evacuating and gas charging apparatus, an exhaust system, a gassupply system, means for successively connecting devices into saidexhaust and gas supply systems for evacuating and gas charging saiddevices, a gas reservoir, a control valve for admitting gas into saidgas supply system from said reservoir, pressure-responsive meansnormally operating said control valve for maintaining the pressure insaid gas supply system within a predetermined operating range, aconstantly operating vacuum pump of substantially greater capacity thansaid gas supply system, a normally closed vacuum valve con trolling asingle connection between said pump and said gas supply system, andmeans for .closing said control valve and opening said vacuum valve inresponse to any abnormal increase in pressure in said gas supply systemabove said operating range, whereby said vacuum pump is efiective forsubstantially immediately evacuating said gas supply system.

17. In evacuating and gas charging apparatus, an exhaust system, a gassupply system, means for successively connecting devices into saidexhaust and gas supply systems for evacuating and gas-(charging saiddevices, a gas reservoir, a control valve for admitting gas into saidgas supply system from said reservoir, means automatically operatingsaid control valve for normally maintain ing the pressure within saidgas supply system within a predetermined operating range, a constantlyoperating vacuum pump of substantially greater capacity than. said gassupply system, a normally closed vacuum valve controlling a connectionbetween said pump andgas supply system, and means automatically closingsaid control valve and opening said vacuum valve in response to anyincrease in pressure in said gas supply system above said operatingrange, whereby said vacuum pump is effective for substantiallyimmediately evacuating said gas supply system, and means automaticallyclosing said vacuum valve and opening said control valve for restoringsaid pressure in said gas supply system to said predetermined 1,763,107Spencer June 10, 1930 2,025,579 Donovan et al Dec. 24, 1935 2,145,830Espersen -s Jan. 31, 1939 2,267,274 Gardner Dec. 23, 1941 2,369,563

Gustin et al Feb. 13, 1945

